The present invention relates to a holder for a collar of a workpiece or tool. More particularly this invention concerns a chuck-type fitting adapted to mount a workpiece or tool for rotation for a machining operation, as in a lathe.
As described in German patent document 4,138,974 filed Nov. 27, 1991 by E. Brangs a holder used with an element such as a tool or workpiece having a mounting collar for rotation of the tool or workpiece about an axis typically has a drive sleeve centered on an axis and shaped to fit coaxially around the collar. A plurality of jaws are displaceable in the sleeve and engageable with the collar to retain the collar in the sleeve. To this end the collar has an inner surface formed with an axially outwardly directed shoulder and the jaws, which have outer ends inside the collar, are formed with axially inwardly directed faces. An actuating element in the holder can spread the jaws to bring their faces to bear axially inward on the shoulders of the collar, and then retract the jaws inward to pull the collar tight to the sleeve. In this manner the collar is locked coaxially to the sleeve so that the sleeve can be rotated to spin the workpiece or tool carrying the collar.
In an automated process the tool or workpiece is mounted on the drive sleeve by an automatic loader which must hold the tool or workpiece in place until the actuator of the holder has spread the jaws. This represents wasted time, as there must be some overlap between when the loader has fitted the tool or workpiece to the sleeve and when the sleeve""s actuator is operated. This time could be more productively used by the loader.
It is therefore an object of the present invention to provide an improved holder for a tool or workpiece having a mounting collar.
Another object is the provision of such an improved holder for a tool or workpiece having a mounting collar which overcomes the above-given disadvantages, that is which allows the tool or workpiece to be secured to the holder without use of the jaws sufficiently that it can be released by the loader.
A tool or workpiece having a mounting collar centered on an axis and formed internally with an axially directed shoulder is mounted on a holder having according to the invention a drive sleeve also centered on an axis and fitted coaxially over the collar and a plurality of angularly spaced jaws in the sleeve having axially outer ends each formed with a rearwardly directed face. The jaws are displaceable radially between an outer locking position with their faces bearing axially inward on the shoulder and an inner freeing position with their faces out of engagement with the collar. An axially displaceable actuating member in the sleeve moves the jaws between their inner and outer positions. Axially extending retaining fingers each have a rear end secured in the sleeve and a front end with a rearwardly directed face. The front ends normally lie in an outer holding position with their faces bearing axially inward on the shoulder and the fingers are elastically deformable into an inner releasing position with their faces out of engagement with the collar.
Thus these fingers, which are a simple structure mounted inside the holder, releasably retain the elementxe2x80x94tool or workpiecexe2x80x94having the mounting collar on the sleeve. Thus the element can be snapped onto and off the sleeve without ay actuation of the jaws, allowing the holder to be loaded and unloaded rapidly. Only during the actual machining operation when, for instance, the tool or workpiece is being rotated is it necessary to use the jaws to retain it in place on the holder.
According to the invention the sleeve is formed with a radially inwardly open jaw groove and the jaws have axially inner ends seated in the jaw groove. A spring ring radially outwardly presses the jaw inner ends into the jaw groove. Similarly the sleeve is formed with a radially inwardly open holder groove. A ring seated in the holder groove is unitarily formed with the fingers which are angularly interleaved with the jaws. These fingers in accordance with the invention are of triangular section each with a radially inwardly directed corner.
Such construction of the sleeve with adjacent grooves, of which the outer groove holding the jaw inner ends is of larger diameter than the inner groove holding the ring or ring segments carrying the fingers, makes assembly of this holder very simple. In fact the inner end faces of the jaws, which taper axially outward, bear on an outer face of the ring or ring segments carrying the fingers and the latching jaws angularly support the holding fingers.